A gas turbine engine may be used to power various types of vehicles and systems. A particular type of gas turbine engine that may be used to power aircraft is a turbofan gas turbine engine. A turbofan gas turbine engine may include, for example, a fan section, a compressor section, a combustor section, a turbine section, and an exhaust section. The fan section induces air from the surrounding environment into the engine and accelerates a fraction of the air toward the compressor section. The remaining fraction of air is accelerated into and through a bypass plenum, and out the exhaust section.
The compressor section, which may include a high pressure compressor and a low pressure compressor, raises the pressure of the air it receives from the fan section to a relatively high level. The compressed air then enters the combustor section, where an annular wall of fuel nozzles injects a steady stream of fuel into a plenum. The injected fuel is ignited to produce high-energy compressed air. The air then flows into and through the turbine section causing turbine blades therein to rotate and generate energy. This energy is used to power the fan and compressor sections. The air exiting the turbine section is exhausted from the engine via the exhaust section, and the energy remaining in the exhaust air aids the thrust generated by the air flowing through the bypass plenum.
In some configurations, the turbine section includes a high pressure turbine section and a low pressure turbine section. An inter-turbine duct may be interposed between the two sections and may include a plurality of radially inwardly extending vanes adapted to guide airflow from the high pressure turbine section into the low pressure turbine section. Conventionally, the vanes and at least part of the inter-turbine duct (e.g., an inner wall or an outer wall of the duct) are cast as a single piece from high-temperature materials, such as nickel-based superalloys. To protect structures surrounding the inter-turbine duct from excessive heat, an insulation blanket is typically disposed around inner diameter of the inter-turbine duct. In other configurations, air flowing through the bypass plenum may be bled into cavities surrounding the inter-turbine duct. However, as the demand for more efficient engines has increased, the demands for increased engine operating temperatures and decreased engine weight have increased as well. As a result, use cooling air flow from the bypass plenum may not provide sufficient cooling for the inter-turbine duct.
Accordingly, it is desirable to have an improved inter-turbine duct, which may have improved performance over conventional inter-turbine ducts when exposed to high engine operating temperatures. In addition, it is desirable for the improved inter-turbine duct to be capable of being retrofitted into existing engines. Moreover, it is desirable for the improved inter-turbine duct to be relatively simple and inexpensive to manufacture. Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.